Surge relief system for watthour meter



Jan. 26, 1960 A. w. PALMER SURGE RELIEF SYSTEM FOR WATTHOUR METER FiledMarch 14, 1958 lnvenior Ansell W Palmer His AHorney 2',9i2,9's3 sURGERELIEF SYSTEM FOR WA'I'IHOUR METER Ansell W. Palmer', Hampton, N.H.,assignor to General Electric Company, a corporation of New YorkApplication March 14, 1958, Serial No. 721,565 5 Claims. (Cl. 324-110)This invention relates generally to protective arrange ments forwatthour meters and more particularly to an improved surge currentrelief system therefor.

Surge current relief systems are intended to protect by lightning, andsuch systems have heretofore been embodied as component parts of thewell-known detachable watthour meters now extensively used by theutility involtages in the order of 240 volts.

It is, therefore, a primary object of this invention to provide a newand improved surge relief system for a watthour meter that willeffectively protect the meter when the line voltages across the meterare on the order of 240 volts.

It is another object of the invention to provide such a new and improvedsystem as a component part of a detachable watthour meter whereineconomy of manudirection to force the surge current out of the gaps andinterrupt further surge current flow.

The invention, together with its objects and advantages, will be bestunderstood upon reference to the following "detailed descriptionthereof, especially when taken in conjunction with the single sheet ofdrawings annexed hereto, in which:

Figure 1 is a plan diagrammatic view of the base of a detachable sel-contained watthour meter showing a plurality of surge relief systemsconstructed in accordance with the teachings of this invention, thecover of the meter being removed and a pair of meter elements beingshown only in outline form for the purpose of orienting the surge reliefsystems relative thereto, and;

Figure 2 is a perspective view of a portion of the base shown in Figure1, showing somewhat diagrammatically an associated meter elementincluding its line and load conductors, and;

Figure 3 is an exploded perspective view of the surge relief system.

The meter shown in Figure 1 includes a base 4, which may be molded froma suitable plastic insulating material, on which A pair of identicalsurge relief systems are shown in Figure 1 at 8, 8', there being one foreach line to which the meter elements 5, 5' are connected, with system 8also providing protection for the third line of a threephase, three-wiresystem.

For a detailed understanding of the surge relief systems, reference willnow be had to the showing of system 8 in Figures 2 and 3. In Figure 2,there is shown the conventional watthour meter element 5 which includesthe potential winding 9 and the current winding 11 mounted on theunitary core 12, all in a manner well known in the art. Since element 5is part of a polyphase meter, one of the lines of a three-phase systemwill be leads and to give this line surge current protection, aninverted L-shaped connector 15 is afiixed to the meter base having itslower extremity suitably connected to the third line terminal (notshown) of the meter.

Located along side of bus 13 is a first surge current carrying conductor16 having its lower end spaced from both the bus 13 and the connector 15to form a first air gap 20 with each. Integral with the upper end ofconductor 16 is a substantially semi-circular mounting flange 17 havinga centrally located aperture 18, a locating car 19 and a projectingportion 21, all of which form a second surge current carrying conductor.The base 4 is sulating member 22, having an aperture 23, on top of surgecurrent carrying conductor 24, which is also provided with an aperture25. Apertures 18, 23, and 25 are aligned to receive the shank of aconducting rivet'26 which passes through aperture 27 in base 4 and isupset to lock all of the parts securely in place.

a and its projection 21, gap 28,

' reinforce one another in Conductor 24 over-hangs projection 21 to forma second air gap 28, and the rivet 26 also clamps in placea ground strapor terminal 29 which provides connection to a ground circuit through themetallic rim 31 of a conventional meter socket. (only a portion of whichis shown in Figure 3). As mentioned above, the watthour meter is of'thedetachable type, conveniently plugging into a meter socket in such a waythat the ground terminal 29 is pressed firmly against rirri 31, all in amanner well known in the art.

It is to be noted that aperture 18 is large enough to allow forseparation between it and the shank of rivet 26, such separation beinglarger than the width of air gap 23. It is also to be noted that bus 13,gap 20, and conductor 16 forms a partially closed loop as does flange 17and conductor 24. That is, and assuming that the gaps 20 and 28 werebridged by conducting elements, the bus 13 and conductor 16 form a firstU-shaped current path and the flange and its projection form withconductor 24 a second U-shaped current path.

With the above arrangement of parts in mind, and with the widths .of theair gaps-20 and 28 correlated to the insulation levels in the variouscomponents of the meter, a surge current passing into the meter throughbus 13 will jump across gap 16 and its associated parts,jurnp pass on toground through conductor 24, rivet 26, ground terminal 29. a

As is best seen in Figure 2, a surge current'coming to the watthourmeter from line terminal 7 will pass downwardly toward the meter throughthe bus 13. -However, when it reaches that part of the bus13 proximateto surge relief gap 2% it will jump the gap to pass through the groundedsurge relief system. After it crosses the gap and enters conductor 16,it will pass upwardly toward across gap 28 and then and by a system thatis extremely compact and inexpensive to manufacture; onethat utilizesminimum space within the meter and derives its magnetic fields by anextremely simple and unique arrangement of parts. I

Therefore, while a particular embodiment 'of the subject invention hasbeen shown and. described herein, it is in the nature ofdescription'rather than limitation, and it will occur to those skilledin the'art that various changes, modifications, and 7 within theprovince of the appended claims, and without departing either in spiritor scope from this invention 20, pass through conductor in its broaderaspects.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is: r

1. For use in a self-contained watthour meter which includes a base, ameter element mounted on the base, a plurality of line terminals mountedon the base for connection of the meter element to line and loadcircuits, and a plurality of line connecting conductors for connectingthe meter element to the line terminals; a surge relief systemcomprising, in combination: a first 'surge current carrying conductorlying adjacent to and spaced from one of the line connecting conductors,said first conductor having one end offset toward the line connectingconductor and spaced therefrom to form a first surge relief air gap,said first conductor and said line connecting conductor being arrangedso that surge currents traveling through the line circuits will pass theupper end o'f'conductor 16 in a direction reverse to its directionthrough bus 13. As it travels through both bus 13 and conductor 16 amagnetic field will be produced around each, and in the gap these fieldswill reinforce one another and be in a direction to force the surgecurrent out 'of the gap., When the surge current leaves the conductor16,'it will pass downwardly through the flange 17 and projection 21,jump the gap 28 and then pass upwardly in conductor 24 from'which,through the conducting rivet 26, it will pass out to the strap 29 afterwhich it will flow to ground. Here again, there is a reversal in thedirection of the current as it flows through the second part ofthe'surge relief system and the magnetic fields surrounding each of theconductors will I i the gap ZSand be in'a direction to force the surgecurrent outof the gap. Thus, when a high energy surge 10,000 volts(peak) or more comes in on bus 13, it will pass to ground via the gaps20 and 2.8, ionizing both gaps in its passage. However, when the240-volt, 60' cycle line current attempts to surge through after theionizing current passes, the first halfcycle of line current willestablish magnetic fields at both gaps of sufficient strength and in theproper direction to force such surge currents out of the gaps and stopthe surging line current 'at the end of the first half-cycle.

Surge reliefsystem S thu's fully protects any surges on thelineconnected to meter element 5 and in a like manner, system 8 will fully.protect the meter from any It has been demonstrated that withsucha'surgerelief of approximately a with the first conductor,

third or common line in a three-phase, threesystem, full protection isavailable for at le'ast five successive 25,000-volt impulses'on a 240volt,60 cycleline powered by a kvaz' transformer delivering .2500 amperes of current. Moreover,'such protection is obtained through the lineterminals along the line connecting conductor across the first surgerelief air gap and then along the first conductor in a directionopposite to the direction of the current through the line connectingconductor whereby the current traverses a closed loop in its flow toproduce a magnetic field in the first surge relief gap in a direction toforce the surge current out of the gap to interrupt its flow, a secondsurge current carrying conductor connected at one end in series a thirdsurge current carrying conductor lying adjacent to and spaced from saidsecond conductor, the other end of the second conductor and one end ofthe third conductor being spaced apart to form relief gap, said secondand third'conrent traverses a second partially closed loop in its flowfield in the second surge relief to produce a magnetic the surge currentout of the gap in a direction to force second surge relief gap tothereby interrupt its flow, and

means adapted for connection of to ground 2. The invention stnaightsection of the the third conductor defined by claim 1 in. which a lineconnecting conductor is adjacent the surge relief system and each of thefirst, second, and third surge current carrying conductors includessubstantially straight sections of conducting material, with. thestraight sections of the first and second conductors being parallel toand aligned with. the straight section of the line connecting conductorand the straight section of the third conductor, respectively, wherebythe first conductor, the straight se tion of the line connectingconductor, and the first surgerelief gap form a substantially U-shapedcurrentpath and the second and third conductors together with the secondrelief gap form a substantially U shaped currentpathn 3. The inventiondefined by claim. 2 in which the first and second conductors are formedas aninteg'ralRpart which includes a flange portion for mounting thispart on the meter base.

4. The. invention defined by'flclairn 3 in which thefiang'e'p'ortioniis'substantially semicircular in shape and includes aradially extending projectioh'which together combinations may be madefirst partially 6 conductor overlies both the flange portion and theprorelief system in place within the watthour meter and jection but isseparated from the flange portion by an inat the same time makeelectrical contact with the third sulating spacing member supportedtherebebween. conductor.

1m definedfi by 1 33 t 5 References Cited in the file of this patentmeans a ap or connec on o e 1r con uc or to ground includes a conductingrivet which extends UNITED STATES PATENTS through the watthour meterbase and through an over- 470,721 Thomson Mar. 15, 1892 size aperture inthe flange portion and is securely con- 2,338,109 Green Jan. 4, 1944nected to the third conductor to both clamp the. surge 2,554,278 TesznerMay 22, 1951 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIONPatent No 2,922,953

January 26, 1960 Ansell W. Palmer read 5 Signed and sealed this 30th dayof August 1960.

' (SEAL) Attest:

Eggylzsr w.. SWIDER UNITED STATES PATENT OFFICE CERTIFICATE OFCORRECTION Patent No. 2,922,953 January 26, 1960 Column 3, line 66 forread 5 Signed and sealed this 30th day of August 1960.

(SEAL) Attest:

W... SWIDER

